The present invention relates to the art of non-invasive examination and internal imaging. It finds particular application in combination with stereotactic surgical procedures and will be described with particular reference thereto. However, it is to be appreciated that the present invention may find other applications in which it is advantageous to orient a patient or examined object relative to images or other representations from previously collected data.
Heretofore, computed tomography scanning has been utilized to assist in various invasive clinical procedures, such as biopsies, the drainage of abscesses, placement of radiation implants, orthopedic pin placement, contrast injections, and the like. In one prior art procedure, the patient was tightly strapped to a patient table mounted on a position control structure for controlledly indexing the patient table through the imaging region of a CT scanner. Based on the reconstructed images from a plurality of planar CT scans, a path for insertion of the needle or probe was determined. Without moving the patient relative to the patient table, the patient table was shifted a preselected precise distance from the imaging region of the CT scanner. The shifting was necessary to provide ready surgical access to the patient without interference from the scanner structure. This shifting of the patient table caused a precisely known offset between the image data and the region of interest of the patient. A guide structure was positioned relative to the patient at the appropriate position and angle to direct a needle or probe through a selected point of entry and along the selected path.
After positioning the needle in the guide, the patient table was shifted such that the region of the patient of interest, the guide, and the needle were repositioned in the examination zone of the CT scanner. More CT scans were made to check the accuracy of the needle positioning relative to the selected path. If necessary, the position or angular orientation of the needle could be adjusted and additional scans taken until an acceptable alignment was achieved. Thereafter, the needle was inserted manually into the patient.
One of the drawbacks of this procedure is that it consumed excessive amounts of expensive, computed tomography scanner time. Because the patient had to be kept at precisely known distances relative to the scanner, the surgery was performed on the scanner associated patient table in the CT scanner room. During the surgery, the scanner was unavailable for performing scanning functions on other patients.
To increase the efficiency of CT scanner utilization, stereotactic fixtures have been developed for performing head and brain surgery remote from the CT scanner. The fixture was rigidly attached to the patient skull prior to the CT scan such that a fixed orientation between the fixture and the skull was maintained even as the patient moved. Reference marks on the fixture provided corresponding reference marks on the resultant images which indicated the relative position and orientation of the fixture and the images.
Thereafter, the patient, with the stereotactic device remaining attached to the skull, was removed to a separate surgical facility freeing the CT scanner for use by other patients. By studying the various images, the doctor planned and calculated an appropriate entry point and path for the needle or probe to follow. Because the relative position of the fixture and the interior head tissue remained fixed, probe guides and distance limiting structures could be selectively positioned on the stereotactic fixture such that the probe or needle would follow the calculated path. See for example U.S. Pat. No. 4,341,220, issued July 27, 1982 to Perry.
One of the drawbacks of the stereotactic fixtures is that their use was limited to areas of the body in which the fixture could be rigidly attached to bone tissue, e.g. the skull. Another drawback to stereotactic fixtures is that they must remain attached between the CT scan and the surgery. The stereotactic fixture could not be reattached with sufficient accuracy to assure the safety of most surgical procedures. For on-going surgical treatment, it was necessary that the fixture be reattached and a new CT scan conducted before each surgical procedure. The repetitive CT scans not only used large amounts of scanner time, but also subjected the patient to numerous doses of radiation.
The present invention provides a new and improved method and apparatus which enables the CT scan data to be realigned with the patient at a subsequent time and a remote location.